Hello m8

The actuator can be tested, but needs to be done with special equipment, ie a pressure gauge and the use of some compressed air. The pipe is taken off the top of the actuator, and air is blown. The pressure shown on the gauge when the spring activates (ie when the bar moves) is the pressuire that the actuator is set to.

Probably best to take actuator off the turbo, and take it to a local friendly gargae (prefferably one with exp with turbo cars).

If you are having trouble with boost, and the actuator is working, on the Cossie, the amal valve (and people messing about with them) can cause most of the trouble. However, I have no idea whether the same setup is used on a RS T

Hope the above helps

JJ